Optimisation of a Caprylic Acid-Based Protocol for IgG Purification from Baboon (Papio anubis) Serum

Abstract

Caprylic acid (CA) fractionation of serum is a simple and cost-effective method of producing high-quality immunoglobulins. While standardised procedures exist for CA purification of IgG for various animals, no published protocol exists for baboon IgG. This study aimed to optimise an efficient protocol for purifying IgG from baboon serum using CA through a stepwise one-factor-at-a-time (OFAT) approach. The effects of serum pH, CA concentration, stirring time and intensity, dialysis buffer, and lyophilisation were evaluated based on the protein content, with SDS-PAGE profiles and albumin-globulin ratios distinguishing IgG from residual albumin. Serum at pH 5.0 with 7% CA (<i>v</i>/<i>v</i>) produced the highest yield, minimising albumin while maximising IgG content. Lower pH (4.0-4.5) and CA (5-6%) reduced protein content, while a higher pH (5.5-6.0) and CA (8-15%) increased protein, but with elevated albumin and contaminants. Stirring serum vigorously at 1200 rpm for 60 min provided effective precipitation of non-IgG proteins. Lower intensities and shorter times resulted in higher albumin and residual proteins, while excessive stirring caused protein denaturation. Dialysis buffer composition had little impact, while lyophilisation significantly enhanced IgG concentration. The optimal protocol involved serum at pH 5.0, 7% CA (<i>v</i>/<i>v</i>), vigorous stirring (1200 rpm) for 60 min, and dialysis against sodium phosphate buffer (pH 7.4) followed by lyophilisation. The resulting IgG enrichment and purity were comparable to commercial-grade products. This study thus established optimal conditions for the purification of baboon IgG with CA, which could be used to support research in this animal model of immunology.